Surface-enhanced Raman scattering is a powerful method used in chemoand biosensorics. The aim of this work was to determine the relationship between the signal of Surface-enhanced Raman scattering and the shape of silver nanostructures under the influence of laser radiation with different power.Plasmonic nanostructures were synthesized in silicon dioxide pores on monocrystalline silicon n-type substrate. The pores were formed using ion-track technology and selective chemical etching. Silver deposition was carried out by galvanic displacement method. Synthesis time was chosen as a parameter that allows controlling the shape of a silver deposit in the pores of silicon dioxide on the surface of single-crystal n-silicon during electrodeless deposition. Deposition time directly effects on the shape of metal nanostructures.Analysis of the dynamics of changing the morphology of the metal deposit showed that as the deposition time increases, the metal evolves from individual metallic crystallites within the pores at a short deposition time to dendritic-like nanostructures at a long time. The dependence of the intensity of Surface-enhanced Raman scattering spectra on the shape of the silver deposit is studied at the powers of a green laser (λ = 532 nm) from 2.5 μW to 150 μW on the model dye analyte Rodamin 6G. The optimum shape of the silver deposit and laser power is analyzed from this point of view design of active surfaces for Surface-enhanced Raman scattering with nondestructive control of small concentrations of substances.The silver nanostructures obtained in porous template SiO2 on n-type silicon substrate could be used as plasmon-active surfaces for nondestructive investigations of substances with low concentrations at low laser powers.

Today, the possibility of amplifying the signal of Raman scattering is intensively studied in order to realize a simple and reliable tool for monitoring of ultra-small concentrations of chemical and biological substances. Plasmon-active nanostructures can serve as the basic element of substrates for signal amplifying, and the degree of amplification is determined by nanostructures size and shape. The formation of nanostructures with a predetermined morphology requires the development of new approaches. In this concern, the paper considers a complex approach of plasmon-active silver nanostructures with a wide range of shapes and sizes formation in the pores of ion-track Sio2templates on silicon. The peculiarities of SiO2templates creation are considered and the etching rates, uniquely determining the parameters of the pores as a function of the etching time, are established. The features of the silver nanostructures formation in the pores of the SiO2template are described for various pore sizes and synthesis regimes (time and solution temperature). The possibility of formation of nanostructures with different shapes as well as evolution of their morphology with variation of synthesis parameters is shown. on the example of dendrites, having a high potential for practical application for amplification of the Raman scattering signal, the possibility of recording Raman spectra was demonstrated using the model analyzer Nile Blue at the concentration of 10-6M/l. The results indicate that plasmon-active silver nanostructures in the pores of ion-track Si02template on silicon can be used as basic element of biosensors to studying ultra-low doses of chemical and biological substances.Communicated by Corresponding Member Valery M. Fedosyuk

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The metal oxide compounds Sr2FeMoO6–d systems with an ordered double perovskite structure due to their unique and extremely important magnetotransport and magnetic properties are among the most promising materials for spintronic devices. In the present work, we investigated the correlation between the citrate-gel synthesis conditions (pH of initial solutions and annealing temperature) and the microstructure, phase transformations and magnetic properties of the Sr2FeMoO6–d nanopowders. According to the results the average grain size of the powders in the dispersion grows from 250 to 550 nm with increasing of pH values. Single-phase nanosized Sr2FeMoO6–d powders had various degrees of superstructural ordering of Fe3+ and Mo5+ (P = 65% for pH = 4, P = 51% for pH = 6 and P = 20 % for pH = 9). With increasing of pH, the Fe2+ concentration increases from 63% to 72%, and the Fe+3 concentration drops from 37% to 28%. According to the results of investigations of magnetization temperature dependence in Sr2FeMoO6–d powders a metastable superparamagnetic state was established at TS<19 K in low-dimensional grains. An optimized synthesis procedure, based on an initial solution of pH = 4, has allowed obtaining a single-phase Sr2FeMoO6–d compound having grain size in the range of 50—120 nm and a superstructural ordering of iron and molybdenum cations of 88%. The optimum conditions of synthesis of nanopowders strontium ferromolybdate allow for the directional change of the phase composition of the synthesized nanosized ceramic with reproducible physical and chemical properties.

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